In COPD, patients' response to treatment can be influenced by disease heterogeneity with some patients showing even distribution of lung damage and others marked differences throughout the lungs. This variation can lead to significant differences in the lung mechanics in different regions with optimal NIV settings for some regions having potentially deleterious effects on neighbouring zones. It has been shown that control of hypoventilation and improved blood gas exchange is essential in order to improve outcomes with NIV in COPD but is less clear if pressure control ventilation as advocated by Windisch and colleagues is required in order to achieve this effect. Inappropriate settings of NIV can also lead to dynamic distension that results in a decrease of tidal volume and an increase in patient discomfort.